Thin film transistor and display unit

ABSTRACT

A thin film transistor with which oxygen is easily supplied to an oxide semiconductor layer and favorable transistor characteristics are able to be restored and a display unit including the same. The thin film transistor includes, sequentially over a substrate, a gate electrode, a gate insulting film, an oxide semiconductor layer including a channel region, and a channel protective layer covering the channel region A source electrode and a drain electrode are formed on the oxide semiconductor layer located on both sides of the channel protective layer, and at least one of the source electrode and the drain electrode has an aperture to expose the oxide semiconductor layer.

RELATED APPLICATION DATA

This application is a division of U.S. patent application Ser. No.12/696,270, filed Jan. 29, 2010, the entirety of which is incorporatedherein by reference to the extent permitted by law. The presentapplication claims priority to Japanese Patent Application JP2009-027646 filed in the Japan Patent Office on Feb. 9, 2009, theentirety of which also is incorporated by reference herein to the extentpermitted by law.

BACKGROUND

The present invention relates to a thin film transistor (TFT) having anoxide semiconductor layer as a channel and a display unit including thesame.

An oxide semiconductor composed of, for example, a zinc oxide, an indiumgallium zinc oxide (IGZO) or the like shows superior characteristics asan active layer of a semiconductor device. In recent years, developmenthas been promoted in an effort to apply the oxide semiconductor to aTFT, a light emitting device, a transparent conducting film or the like.

For example, in the TFT including the oxide semiconductor, electronmobility is high and its electric characteristics are superior comparedto the existing TFT including amorphous silicon (a-Si: H) used for aliquid crystal display unit as a channel. Further, the TFT including theoxide semiconductor has an advantage that high mobility is able to beexpected even at low temperature around room temperature.

Meanwhile, it has been known that in the oxide semiconductor, the heatresistance is not sufficient, and thus due to heat treatment in amanufacturing process of the TFT, oxygen, zinc and the like are detachedand lattice defect is formed. The lattice defect results in forming anelectrically shallow impurity level, and causes low resistance of theoxide semiconductor layer. This results in normally-on type operation,that is depression type operation in which a drain current is flownwithout applying a gate voltage, the threshold voltage is decreased asthe defect level is increased, and the leakage current is increased.

Thus, in the past, it has been known that oxygen annealing is performedunder high temperature after a TFT is formed and thereby oxygen issupplied to an absent portion in which oxygen is lacked or oxygen isdetached in the oxide semiconductor layer to restore the characteristicsas described in, for example, Japanese Unexamined Patent ApplicationPublication Nos. 2006-15529 and 2006-165532.

SUMMARY OF THE INVENTION

However, there has been a disadvantage that the transistorcharacteristics are hardy restored according to the shape and the sizeof a TFT.

It is desirable to provide a thin film transistor with which oxygen iseasily supplied to an oxide semiconductor layer and favorable transistorcharacteristics are able to be restored, and a display unit includingthe thin film transistor.

According to an embodiment of the invention, there is provided a firstthin film transistor including sequentially over a substrate: a gateelectrode; a gate insulting film; an oxide semiconductor layer includinga channel region; and a channel protective layer covering the channelregion, in which a source electrode and a drain electrode are formed onthe oxide semiconductor layer located on both sides of the channelprotective layer, and at least one of the source electrode and the drainelectrode has an aperture to expose the oxide semiconductor layer.

According to an embodiment of the invention, there is provided a secondthin film transistor including sequentially over a substrate: a gateelectrode; a gate insulting film; an oxide semiconductor layer includinga channel region; and a channel protective layer covering the channelregion, wherein a source electrode and a drain electrode are formed onthe oxide semiconductor layer located on both sides of the channelprotective layer, and the source electrode and the drain electrode areisolated in a channel width direction by a groove to expose the oxidesemiconductor layer. The channel width direction is a width in adirection perpendicular to a direction in which the source electrode andthe drain electrode are opposed (in general, a longitudinal direction).

According to an embodiment of the invention, there is provided a thirdthin film transistor including sequentially over a substrate: a gateelectrode; a gate insulting film; an oxide semiconductor layer includinga channel region; and a channel protective layer covering the channelregion, in which a source electrode and a drain electrode are formed onthe oxide semiconductor layer located on both sides of the channelprotective layer, and a protrusion region in which the oxidesemiconductor layer is exposed from an end of the source electrode orthe drain electrode is provided along a side opposed to a sideoverlapped with the channel protective layer of at least one of thesource electrode and the drain electrode.

A first to a third display units according to the embodiment of theinvention include a thin film transistor and a display device, in whichthe thin film transistors thereof are respectively composed of the firstto the third thin film transistors.

In the first thin film transistor of the embodiment of the invention,the aperture to expose the oxide semiconductor layer is provided in atleast one of the source electrode and the drain electrode. Thus, in thecase where oxygen annealing is provided under high temperature afterforming the thin film transistor, oxygen is easily supplied from theaperture to an absent portion in which oxygen is lacked or oxygen isdetached in the oxide semiconductor layer.

In the second thin film transistor of the embodiment of the invention,the source electrode and the drain electrode are isolated in the channelwidth direction by the groove to expose the oxide semiconductor layer.Thus, in the case where oxygen annealing is provided under hightemperature after forming the thin film transistor, oxygen is easilysupplied from the groove to an absent portion in which oxygen is lackedor oxygen is detached in the oxide semiconductor layer.

In the third thin film transistor of the embodiment of the invention,the protrusion region in which the oxide semiconductor layer is exposedfrom the end of the source electrode or the drain electrode is providedalong the side opposed to the side overlapped with the channelprotective layer of at least one of the source electrode and the drainelectrode. Thus, in the case where oxygen annealing is provided underhigh temperature after forming the thin film transistor, oxygen iseasily supplied from the protrusion region to an absent portion in whichoxygen is lacked or oxygen is detached in the oxide semiconductor layer.

The first to the third display units of the embodiment of the inventionrespectively include the first to the third thin film transistors of theembodiment of the invention. Thus, low resistance of the oxidesemiconductor layer of the thin film transistor is inhibited and thusthe leakage current is suppressed, and light display with high luminanceis enabled.

According to the first thin film transistor of the embodiment of theinvention, the aperture to expose the oxide semiconductor layer isprovided in at least one of the source electrode and the drainelectrode. Thus, oxygen is able to be easily supplied from the apertureto the oxide semiconductor layer, and favorable transistorcharacteristics are able to be restored.

In the second thin film transistor of the embodiment of the invention,the source electrode and the drain electrode are isolated in the channelwidth direction by the groove to expose the oxide semiconductor layer.Thus, oxygen is easily supplied from the groove to the oxidesemiconductor layer, and favorable transistor characteristics are ableto be restored.

In the third thin film transistor of the embodiment of the invention,the protrusion region in which the oxide semiconductor layer is exposedfrom the end of the source electrode or the drain electrode is providedalong the side opposed to the side overlapped with the channelprotective layer of at least one of the source electrode and the drainelectrode. Thus, oxygen is easily supplied from the protrusion region tothe oxide semiconductor layer, and favorable transistor characteristicsare able to be restored.

The first to the third display units of the embodiment of the inventionrespectively include the first to the third thin film transistors of theembodiment of the invention. Thus, low resistance of the oxidesemiconductor layer of the thin film transistor is inhibited and thusthe leakage current is able to be suppressed, and light display withhigh luminance is enabled.

Other and further objects, features and advantages of the invention willappear more fully from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a configuration of a display unitaccording to a first embodiment of the invention.

FIG. 2 is an equivalent circuit diagram illustrating an example of thepixel drive circuit illustrated in FIG. 1.

FIG. 3 is a plan view illustrating a structure of the TFT illustrated inFIG. 2.

FIG. 4 is a cross sectional view taken along line IV-IV of FIG. 3.

FIG. 5 is a cross sectional view illustrating a structure of the displayregion illustrated in FIG. 1.

FIG. 6A to 6D are cross sectional views illustrating a method ofmanufacturing the display unit illustrated in FIG. 1 in the order ofsteps.

FIGS. 7A and 7B are diagrams for explaining characteristics of the TFTillustrated in FIG. 3.

FIG. 8 is a plan view illustrating a structure of a TFT according toModified example 1-1.

FIG. 9 is a cross sectional view illustrating a structure of the TFTillustrated in FIG. 8.

FIG. 10 is a plan view illustrating a configuration of a pixel circuitincluding the TFT illustrated in FIG. 8.

FIG. 11 is a plan view illustrating a structure of a TFT according toModified example 1-2.

FIG. 12 is a cross sectional view illustrating a structure of the TFTillustrated in FIG. 11.

FIG. 13 is a plan view illustrating a configuration of a pixel circuitincluding the TFT illustrated in FIG. 11.

FIG. 14 is a plan view illustrating a structure of a TFT according toModified example 1-3.

FIG. 15 is a cross sectional view illustrating a structure of the TFTillustrated in FIG. 14.

FIG. 16 is a plan view illustrating a modified example of the TFTillustrated in FIG. 14.

FIG. 17 is a plan view illustrating a configuration of a pixel circuitincluding the TFT illustrated in FIG. 14.

FIG. 18 is a plan view illustrating a configuration of a pixel circuitaccording to Modified example 1-4.

FIG. 19 is a plan view illustrating an enlarged configuration of thedrive transistor illustrated in FIG. 18.

FIG. 20 is a plan view illustrating a configuration of a pixel circuitaccording to Modified example 1-5.

FIG. 21 is a cross sectional view illustrating a configuration of thedrive transistor and the retentive capacity illustrated in FIG. 20.

FIG. 22 is a plan view illustrating a structure of a TFT according to asecond embodiment of the invention.

FIG. 23 is a cross sectional view taken along line XXIII-XXIII of FIG.22.

FIG. 24 is a plan view for explaining an oxygen transfer distance in thecase of W=20 μm and L=10 μm in Table 1.

FIG. 25 is a plan view for explaining an oxygen transfer distance in thecase of W=50 μm and L=10 μm in Table 1.

FIG. 26 is a diagram illustrating respective transistor characteristicsin the case of W=20 μm and L=20 μm (favorable) and in the case of W=20μm and L=20 μm (conductor operation) in Table 1.

FIG. 27 is a plan view illustrating a structure of a TFT according to athird embodiment of the invention.

FIG. 28 is a plan view illustrating a structure of a TFT according toModified example 3-1.

FIG. 29 is a cross sectional view illustrating a structure of the TFTillustrated in FIG. 28.

FIG. 30 is a plan view illustrating a configuration of a pixel circuitaccording to Modified example 3-2.

FIG. 31 is a cross sectional view illustrating a configuration of thesampling transistor illustrated in FIG. 30.

FIG. 32 is a plan view illustrating a configuration of a pixel circuitaccording to Modified example 3-3.

FIG. 33 is a cross sectional view illustrating a configuration of thesampling transistor illustrated in FIG. 32.

FIG. 34 is a plan view illustrating a schematic structure of a moduleincluding the display unit of the foregoing embodiments.

FIG. 35 is a perspective view illustrating an appearance of a firstapplication example of the display unit of the foregoing embodiments.

FIG. 36A is a perspective view illustrating an appearance viewed fromthe front side of a second application example, and FIG. 36B is aperspective view illustrating an appearance viewed from the rear side ofthe second application example.

FIG. 37 is a perspective view illustrating an appearance of a thirdapplication example.

FIG. 38 is a perspective view illustrating an appearance of a fourthapplication example.

FIG. 39A is an elevation view of a fifth application example unclosed,FIG. 39B is a side view thereof, FIG. 39C is an elevation view of thefifth application example closed, FIG. 39D is a left side view thereof,FIG. 39E is a right side view thereof, FIG. 39F is a top view thereof,and FIG. 39G is a bottom view thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the invention will be hereinafter described in detailwith reference to the drawings. The description will be given in thefollowing order:

-   -   1. First embodiment (example that an aperture is provided in a        source electrode and a drain electrode);    -   2. Second embodiment (example that the source electrode and the        drain electrode are isolated by a groove); and    -   3. Third embodiment (example that a protrusion region is        provided outside the source electrode and the drain electrode).

1. First Embodiment

FIG. 1 illustrates a configuration of a display unit according to afirst embodiment of the invention. The display unit is used as anultrathin organic light emitting color display unit or the like. In thedisplay unit, for example, a display region 110 in which pixels PXLCscomposed of a plurality of organic light emitting devices 10R, 10G, and10B described later are arranged in a matrix state as a display deviceis formed in an after-mentioned TFT substrate 1. On the periphery of thedisplay region 110, a horizontal selector (HSFL) 121 as a signalsection, and a write scanner (WSCN) 131 and a power source scanner(DSCN) 132 as a scanner section are formed.

In the display region 110, signal lines DTL 101 to DTL 10 n are arrangedin the column direction, and scanning lines WSL 101 to WSL 10 m andpower source lines DSL 101 to DSL 10 m are arranged in the rowdirection. A pixel circuit 140 including the organic light emittingdevice PXLC (one of 10R, 10G, and 10B (sub pixel)) is provided at eachcross section between each signal line DTL and each scanning line WSL.Each signal line DTL is connected to the horizontal selector 121. Avideo signal is supplied from the horizontal selector 121 to the signalline DTL. Each scanning line WSL is connected to the write scanner 131.Each power source line DSL is connected to the power source line scanner132.

FIG. 2 illustrates an example of the pixel circuit 140. The pixelcircuit 140 is an active drive circuit having a sampling transistor 3A,a drive transistor 3B, a retentive capacity 3C, and a light emittingdevice 3D composed of the organic light emitting device PXLC. In thesampling transistor 3A, its gate is connected to the correspondingscanning line WSL 101, one of its source and its drain is connected tothe corresponding signal line DTL 101, and the other thereof isconnected to a gate g of the drive transistor 3B. In the drivetransistor 3B, its drain d is connected to the corresponding powersource line DSL101, and its source s is connected to an anode of thelight emitting device 3D. A cathode of the light emitting device 3D isconnected to a ground wiring 3H. The ground wiring 3H is commonly wiredto all pixels PXLCs. The retentive capacity 3C is connected between thesource s and the gate g of the drive transistor 3B.

The sampling transistor 3A makes conduction in accordance with a controlsignal supplied from the scanning line WSL101, performs sampling of asignal potential of a video signal supplied from the signal line DTL101,and retains the result into the retentive capacity 3C. The drivetransistor 3B receives a current supply from the power source lineDSL101 in the first potential, and supplies a drive current to the lightemitting device 3D in accordance with the signal potential retained inthe retentive capacity 3C. The light emitting device 3D emits light atluminance in accordance with the signal potential of the video signal bythe supplied drive current.

FIG. 3 illustrates a planar structure of a TFT 20 configuring thesampling transistor 3A and the drive transistor 3B illustrated in FIG.2. FIG. 4 illustrates a cross sectional structure taken along line IV-IVof FIG. 3. The TFT 20 is an oxide semiconductor transistor sequentiallyhaving, for example, a gate electrode 21, a gate insulating film 22, anoxide semiconductor layer 23, a channel protective layer 24, a sourceelectrode 25S, a drain electrode 25D, and a passivation film 26 over asubstrate 10. The oxide semiconductor represents an oxide of zinc,indium, gallium, tin, or a mixture thereof, and is known to showsuperior semiconductor characteristics.

The gate electrode 21 controls an electron density in the oxidesemiconductor layer 23 by a gate voltage applied to the TFT 20. The gateelectrode 21 has, for example, a two-layer structure composed of amolybdenum (Mo) layer having a thickness of 50 nm and an aluminum (Al)layer or an aluminum alloy layer having a thickness of 400 nm. Examplesof aluminum alloy layers include an aluminum-neodymium alloy layer.

The gate insulating film 22 has, for example, a thickness of about 400nm and is made of a silicon oxide film, a silicon nitride film, asilicon oxynitride film, an aluminum oxide film, or a laminated filmthereof.

The oxide semiconductor layer 23 has, for example, a thickness from 20nm to 100 nm both inclusive, and is composed of indium gallium zincoxide (IGZO).

The channel protective layer 24 is preferably a layer that makes anoxygen amount detached from the oxide semiconductor thin film layer 23small and that supplies a small amount of hydrogen to the oxidesemiconductor thin film layer 23. The channel protective layer 24 has,for example, a thickness of about 200 nm, and is made of a silicon oxidefilm, a silicon nitride film, a silicon oxynitride film, an aluminumoxide film, or a laminated film thereof.

The source electrode 25S and the drain electrode 25D are formed on theoxide semiconductor layer 23 located on both sides of the channelprotective layer 24. In the oxide semiconductor layer 23, a sectioncorresponding to a region between the source electrode 25S and the drainelectrode 25D is a channel region 23A. The channel region 23A is coveredwith the channel protective layer 24. Further, both sides in the channelwidth direction of the oxide semiconductor layer 23 are an exposedportion 23B not covered with the channel protective layer 24, the sourceelectrode 25S or the drain electrode 25D.

The source electrode 25S and the drain electrode 25D have an aperture 27to expose the oxide semiconductor layer 23. Thereby, in the TFT 20,oxygen is easily supplied to the oxide semiconductor layer 23, and isable to restore favorable transistor characteristics.

The aperture 27 may be provided in one of the source electrode 25S andthe drain electrode 25D. Further, the dimension of the aperture 27, theshape thereof, and the number thereof are not particularly limited. Forexample, the aperture 27 having dimensions of 5 μm*5 μm may be arrangedin four locations on one side.

The source electrode 25S and the drain electrode 25D include, forexample, a metal layer containing aluminum, copper, silver, ormolybdenum as a main component. The source electrode 25S and the drainelectrode 25D are preferably made of a single layer film of the metallayer, or a laminated film composed of the metal layer and a metal layeror metal compound layer containing titanium, vanadium, niobium,tantalum, chromium, tungsten, nickel, zinc, or indium as a maincomponent.

In particular, the source electrode 25S and the drain electrode 25Dpreferably include a metal layer containing aluminum or copper as a maincomponent, since thereby resistance of the wirings is able to belowered. Examples of metals having aluminum as a main component includealuminum, an aluminum-neodymium alloy, and aluminum containing silicon.

Further, a layer contacted with the oxide semiconductor layer 23 of thesource electrode 25S and the drain electrode 25D is preferably composedof a metal that does not make oxygen detached from the oxidesemiconductor layer 23 or a metal compound that does not make oxygendetached from the oxide semiconductor layer 23, since with the use ofsuch a metal or such a metal compound, there is a small possibility tochange the electric characteristics of the TFT 20. Specifically, thelayer contacted with the oxide semiconductor layer 23 of the sourceelectrode 25S and the drain electrode 25D is preferably composed ofmolybdenum; an oxide, a nitride, or a nitroxide of molybdenum ortitanium; an aluminum nitride; or a copper oxide.

The uppermost layer of the source electrode 25S and the drain electrode25D is preferably composed of titanium; or an oxide, a nitride, or anitroxide of titanium.

As a specific structural example of the source electrode 25S and thedrain electrode 25D, for example, a laminated film in which a molybdenumlayer 25A having a thickness of 50 nm, an aluminum layer 25B having athickness of 50 nm, and a titanium layer 25C having a thickness of 50 nmare layered from the oxide semiconductor layer 23 side is preferable forthe following reason. In the case where an anode 52 of the organic lightemitting devices 10R, 10G, and 10B described later is composed of ametal containing aluminum as a main component, the anode 52 should beprovided with wet etching by using a mixed solution containingphosphoric acid, nitric acid, acetic acid or the like. At this time, thetitanium layer 25C as the uppermost layer has a significantly lowetching rate, and thus the titanium layer 25C is able to be left on thesubstrate 10 side. As a result, a cathode 55 of the organic lightemitting devices 10R, 10G, and 10B described later is allowed to beconnected to the titanium layer 25C on the substrate 10 side.

Otherwise, the layer contacted with the oxide semiconductor layer 23 ofthe source electrode 25S and the drain electrode 25D is preferablycomposed of a metal oxide or a metal nitride. Examples of metal oxidesinclude titanium oxide, niobium oxide, zinc oxide, tin oxide, and ITO(indium tin composite oxide). Examples of metal nitrides includetitanium nitride and tantalum nitride.

The passivation film 26 has, for example, a thickness of about 300 nm,and is made of a silicon oxide film, a silicon nitride film, a siliconoxynitride film, an aluminum oxide film, or a laminated film thereof.

FIG. 5 illustrates a cross sectional structure of the display region110. In the display region 110, the organic light emitting device 10Rgenerating red light, the organic light emitting device 10G generatinggreen light, and the organic light emitting device 10B generating bluelight are sequentially formed in a matrix state as a whole. The organiclight emitting devices 10R, 10G, and 10B have a reed-like planar shape,and a combination of the organic light emitting devices 10R, 10G, and10B adjacent to each other composes one pixel.

The organic light emitting devices 10R, 10G, and 10B respectively have astructure in which the anode 52, an interelectrode insulating film 53,an organic layer 54 including an after-mentioned light emitting layer,and the cathode 55 are layered in this order over the TFT substrate 1with a planarizing insulating film 51 in between.

The organic light emitting devices 10R, 10G, and 10B as above are coatedwith a protective film 56 composed of silicon nitride (SiN), siliconoxide (SiO) or the like according to needs. Further, a sealing substrate71 made of glass or the like is bonded to the whole area of theprotective film 56 with an adhesive layer 60 made of a thermoset resin,an ultraviolet curable resin or the like in between, and thereby theorganic light emitting devices 10R, 10G, and 10B are sealed. The sealingsubstrate 71 may be provided with a color filter 72 and a lightshielding film (not illustrated) as a black matrix according to needs.

The planarizing insulating film 51 is intended to planarize a front faceof the TFT substrate 1 over which the pixel circuit 140 including thesampling transistor 3A and the drive transistor 3B composed of theforegoing TFT 20 is formed. Since a fine connection hole 51A is formedin the planarizing insulating film 51, the planarizing insulating film51 is preferably made of a material having favorable pattern precision.Examples of materials of the planarizing insulating film 51 include anorganic material such as polyimide and an inorganic material such assilicon oxide (SiO₂). The drive transistor 3B illustrated in FIG. 2 iselectrically connected to the anode 52 through the connection hole 51Aprovided in the planarizing insulating film 51.

The anode 52 is formed correspondingly to the respective organic lightemitting devices 10R, 10G, and 10B. Further, the anode 52 has a functionas a reflecting electrode to reflect light generated in the lightemitting layer, and desirably has high reflectance as much as possiblein order to improve light emitting efficiency. The anode 52 has, forexample, a thickness from 100 nm to 1000 nm both inclusive. The anode 52is composed of a simple substance or an alloy of a metal element such assilver (Ag), aluminum (Al), chromium (Cr), titanium (Ti), iron (Fe),cobalt (Co), nickel (Ni), molybdenum (Mo), copper (Cu), tantalum (Ta),tungsten (W), platinum (Pt), and gold (Au).

The interelectrode insulating film 53 is intended to secure insulationbetween the anode 52 and the cathode 55, and to accurately obtain adesired shape of the light emitting region. For example, theinterelectrode insulating film 53 is made of an organic material such aspolyimide or an inorganic insulating material such as silicon oxide(SiO₂). The interelectrode insulating film 53 has aperturescorrespondingly to the light emitting region of the anode 52. Theorganic layer 54 and the cathode 55 may be also provided continuously onthe interelectrode insulating film 53 in addition to on the lightemitting region, but light is emitted only in the aperture of theinterelectrode insulating film 53.

The organic layer 54 has, for example, a structure in which a holeinjection layer, a hole transport layer, the light emitting layer, andan electron transport layer (not illustrated) are layered sequentiallyfrom the anode 52 side. Of the foregoing layers, the layers other thanthe light emitting layer may be provided according to needs. Further,the organic layer 54 may have a structure varying according to the lightemitting color of the organic light emitting devices 10R, 10G, and 10B.The hole injection layer is intended to improve the electron holeinjection efficiency and functions as a buffer layer to prevent leakage.The hole transport layer is intended to improve efficiency to transportelectron hole into the light emitting layer. The light emitting layer isintended to generate light due to electron-hole recombination byimpressing an electric field. The electron transport layer is intendedto improve efficiency to transport electrons into the light emittinglayer. The materials of the organic layer 54 are not particularlylimited as long as the materials are a general low molecular organicmaterial or a general high molecular organic material.

The cathode 55 has, for example, a thickness from 5 nm to 50 nm bothinclusive, and is composed of a simple substance or an alloy of metalelements such as aluminum (Al), magnesium (Mg), calcium (Ca), and sodium(Na). Specially, an alloy of magnesium and silver (MgAg alloy) or analloy of aluminum (Al) and lithium (Li) (AlLi alloy) is preferable.Further, the cathode 55 may be composed of ITO or IZO (indium zinccomposite oxide).

The display unit may be manufactured, for example, as follows.

Step of Forming TFT Substrate 1

First, as illustrated in FIG. 6A, a metal layer that has the foregoingthickness and is made of the foregoing material is formed on thesubstrate 10 made of glass by, for example, sputtering method.Photolithography and etching are provided for the metal layer, andthereby the gate electrode 21 is formed.

Next, as illustrated in FIG. 6B, the gate insulating film 22 that hasthe foregoing thickness and is made of the foregoing material is formedon the whole area of the substrate 10 by, for example, plasma CVD(Chemical Vapor Deposition) method.

Subsequently, again as illustrated in FIG. 6B, the oxide semiconductorlayer 23 that has the foregoing thickness and is made of the foregoingmaterial is formed by sputtering method. Specifically, in the case wherethe oxide semiconductor layer 23 is composed of indium gallium zincoxide (IGZO), for example, with the use of DC sputtering method in whichIGZO ceramics is used as a target, an IGZO film is formed on thesubstrate 10 by plasma discharge by mixed gas of argon (Ar) and oxygen(O₂). Before plasma discharge, air is exhausted until the vacuum degreein a vacuum container becomes equal to or less than 1*10⁻⁴ Pa, and thenthe mixed gas of argon and oxygen is introduced. In the case where theoxide semiconductor layer 23 is composed of zinc oxide, with the use ofRF sputtering method in which zinc oxide ceramics is used as a target orwith the use of DC sputtering method in which zinc metal target is usedin gas atmosphere containing argon and oxygen, a zinc oxide film isformed.

After that, as illustrated in FIG. 6C, the oxide semiconductor layer 23is formed into a given shape by photolithography and etching.Subsequently, again as illustrated in FIG. 6C, the channel protectivelayer 24 that has the foregoing thickness and is made of the foregoingmaterial is formed by, for example, plasma CVD method. The channelprotective layer 24 is formed into a given shape by photolithography andetching.

After the channel protective layer 24 is formed, for example, bysputtering method, the molybdenum layer 25A having a thickness of 50 nm,the aluminum layer 25B having a thickness of 50 nm, and the titaniumlayer 25C having a thickness of 50 nm are formed. Subsequently, afterthe titanium layer 25C is etched by dry etching with the use ofchlorine-based gas, the aluminum layer 25B and the molybdenum layer 25Aare etched by wet etching with the use of a mixed solution containingphosphoric acid, nitric acid, and acetic acid. Thereby, as illustratedin FIG. 6D, the source electrode 25S and the drain electrode 25D havingthe aperture 27 are formed.

After the source electrode 25S and the drain electrode 25D are formed,oxygen annealing is provided under high temperature, and thereby oxygenis supplied to an absent portion in which oxygen is lacked or oxygen isdetached in the oxide semiconductor layer 23 to restore thecharacteristics. As annealing conditions, for example, annealing in theatmosphere in which the nitrogen concentration is 60% and the oxygenconcentration is 40% at 300 deg C. in 1 hour may be adopted. In thiscase, the aperture 27 is provided in the source electrode 25S and thedrain electrode 25D, and the oxide semiconductor layer 23 is exposed inthe aperture 27. Thus, oxygen is easily supplied from the aperture 27 tothe oxygen absent portion in the oxide semiconductor layer 23. Further,oxygen is also easily supplied from the exposed portion 23B of the oxidesemiconductor layer 23 to the oxide semiconductor layer 23.

After that, the passivation film 26 that has the foregoing thickness andis made of the foregoing material is formed by atomic layer depositionmethod or sputtering method. Accordingly, the TFT substrate 1 having theTFT 20 illustrated in FIG. 3 and FIG. 4 is formed.

The TFT 20 was actually fabricated by forming the source electrode 25Sand the drain electrode 25D as a laminated film composed of themolybdenum layer 25A having a thickness of 50 nm, the aluminum layer 25Bhaving a thickness of 500 nm, and the titanium layer 25C having athickness of 50 nm, and annealing the resultant film under the foregoingannealing conditions. For the obtained TFT 20, transfer characteristicswere examined. In the result, as illustrated in FIG. 7A, transistorcharacteristics in which on/off ratio was sufficiently secured wereobtained.

Meanwhile, a TFT was fabricated in the same manner as the foregoingmanner, except that a titanium layer was used instead of the molybdenumlayer 25A. For the obtained TFT, the transfer characteristics wereexamined In the result, as illustrated in FIG. 7B, transistorcharacteristics in which on/off ratio was sufficiently secured were notobtained.

The reason of the foregoing result may be as follows. In the case wherethe source electrode 25S and the drain electrode 25D are formed as athree-layer film composed of titanium, aluminum, and titanium, titaniumis hardly wet-etched and thus dry etching is generally used. To obtainfavorable TFT characteristics, the thickness of the oxide semiconductorlayer 23 should be about 50 nm. However, in the case of using dryetching, the selection ratio between the metal material composing thesource electrode 25S and the drain electrode 25D and the oxidesemiconductor is difficult to increase. Thus, in etching the sourceelectrode 25S and the drain electrode 25D, the oxide semiconductor layer23 is eliminated. Therefore, the oxide semiconductor layer 23 is notexposed in the aperture 27, and oxygen is difficult to be supplied intothe oxide semiconductor layer 23 even if oxygen annealing is performed.

Step of Forming Organic Light Emitting Devices 10R, 10G, And 10B

After the TFT substrate 1 is formed, the whole area of the TFT substrate1 is coated with a photosensitive resin, and exposure and developmentare performed. Thereby, the planarizing insulating film 51 and theconnection hole 51A are formed and fired. Next, the anode 52 made of theforegoing material is formed by, for example, direct current sputtering.The resultant film is selectively etched and patterned into a givenshape by, for example, using lithography technique. Subsequently, theinterelectrode insulating film 53 that has the foregoing thickness andis made of the foregoing material is formed by, for example, CVD method,and an aperture is formed by using, for example, lithography technique.After that, the organic layer 54 and the cathode 55 that are made of theforegoing materials are sequentially formed by, for example, evaporationmethod to form the organic light emitting devices 10R, 10G, and 10B.Subsequently, the organic light emitting devices 10R, 10G, and 10B arecovered with the protective film 56 made of the foregoing material.

After that, the adhesive layer 60 is formed on the protective film 56.After that, the sealing substrate 71 that is provided with the colorfilter 72 and is made of the foregoing material is prepared. The TFTsubstrate 1 and the sealing substrate 71 are bonded to each other withthe adhesive layer 60 in between. Accordingly, the display unitillustrated in FIG. 5 is completed.

In this display unit, the sampling transistor 3A makes conduction inaccordance with a control signal supplied from the scanning line WSL, asignal potential of a video signal supplied from the signal line DTL issampled and retained in the retentive capacity 3C. Further, a current issupplied from the power source line DSL in the first potential to thedrive transistor 3B, and a drive current is supplied to the lightemitting device 3D (organic light emitting devices 10R, 10G, and 10B) inaccordance with the signal potential retained in the retentive capacity3C. The light emitting device 3D (organic light emitting devices 10R,10G, and 10B) emits light at luminance corresponding to the signalpotential of the video signal by the supplied drive current. The lightis transmitted through the cathode 55, the color filter 72, and thesealing substrate 71 and is extracted.

In this case, in the TFT 20 configuring the sampling transistor 3A andthe drive transistor 3B, the aperture 27 to expose the oxidesemiconductor layer 23 is provided in the source electrode 25S and thedrain electrode 25D. Thus, by oxygen annealing in the manufacturingstep, oxygen is supplied from the aperture 27 to the absent portion inwhich oxygen is lacked or oxygen is detached in the oxide semiconductorlayer 23, and transistor characteristics are sufficiently restored.Accordingly, in the display unit configured by using the TFT 20, lowresistance of the oxide semiconductor layer 23 of the TFT 20 issuppressed, the leakage current is suppressed, and light display withhigh luminance is enabled.

As described above, in this embodiment, the aperture 27 to expose theoxide semiconductor layer 23 is provided in the source electrode 25S andthe drain electrode 25D of the TFT 20. Thus, oxygen is easily suppliedfrom the aperture 27 to the oxide semiconductor layer 23, and favorablytransistor characteristics are able to be restored. Accordingly, when adisplay unit is configured by using the TFT 20, low resistance of theoxide semiconductor layer 23 of the TFT 20 is suppressed and thus theleakage current is able to be suppressed, and light display with highluminance is enabled.

Descriptions will be hereinafter given of Modified examples 1-1 to 1-5of this embodiment. In an actual pixel layout, in some cases, it isdifficult to provide the aperture 27 in the source electrode 25S or thedrain electrode 25D in the line and space process. The followingmodified examples are able to resolve such a disadvantage.

Modified Example 1-1

FIG. 8 illustrates a planar structure of the TFT 20 according toModified example 1-1. FIG. 9 illustrates a cross sectional structuretaken along line IX-IX of FIG. 8. In the TFT 20, a channel width Wd ofthe drain electrode 25D is different from a channel width Ws of thesource electrode 25S, and the aperture 27 to expose the oxidesemiconductor layer 23 is provided on both sides in the channel widthdirection of one of the source electrode 25S and the drain electrode25D. Thereby, in the TFT 20, oxygen is easily supplied to the oxidesemiconductor layer 23, and favorable transistor characteristics areable to be restored.

Specifically, it is preferable that the channel width Ws of the sourceelectrode 25S is larger than the channel width Wd of the drain electrode25D, and the aperture 27 is provided on both sides in the channel widthdirection of the drain electrode 25D. If the aperture 27 is provided inthe source electrode 25S, it is difficult to sufficiently secure theretentive capacity 3C.

FIG. 10 illustrates a planar structure of the pixel circuit 140 usingthe TFT 20 illustrated in FIG. 8 and FIG. 9. The TFT 20 is applicable toboth the sampling transistor 3A and the drive transistor 3B, but inparticular, is preferably applied to the drive transistor 3B, since thedrive transistor 3B has a large transistor size.

Modified Example 1-2

FIG. 11 illustrates a planar structure of the TFT 20 according toModified example 1-2. FIG. 12 illustrates a cross sectional structuretaken along line XII-XII of FIG. 11. In the TFT 20, one of the drainelectrode 25D and the source electrode 25S is in the shape of a nozzleor in the shape of tooth. The aperture 27 to expose the oxidesemiconductor layer 23 is provided between each teeth of the comb.Thereby, in the TFT 20, oxygen is easily supplied to the oxidesemiconductor layer 23, and favorable transistor characteristics areable to be restored.

Specifically, it is preferable that the drain electrode 25D is in theshape of a nozzle or in the shape of a comb having many teeth 25D1, andthe aperture 27 is provided between the respective teeth 25D1 of thedrain electrode 25D. If the aperture 27 is provided in the sourceelectrode 25S, it is difficult to sufficiently secure the retentivecapacity 3C. Further, the channel width Wd of the drain electrode 25D isequal to the total of each width of the respective teeth 25D1(Wd=Wd1+Wd2+ . . . Wdn). The channel width Ws of the source electrode25S is larger than the channel width Wd of the drain electrode 25D.

FIG. 13 illustrates a planar structure of the pixel circuit 140 usingthe TFT 20 illustrated in FIG. 11 and FIG. 12. The TFT 20 is applicableto both the sampling transistor 3A and the drive transistor 3B, but inparticular, is preferably applied to the drive transistor 3B, since thedrive transistor 3B has a large transistor size.

Modified Example 1-3

FIG. 14 illustrates a planar structure of the TFT 20 according toModified example 1-3. FIG. 15 illustrates a cross sectional structuretaken along line XV-XV of FIG. 14. In the TFT 20, a narrow channel widthregion 25D2 in which the channel width is decreased is provided in thedrain electrode 25D. The aperture 27 to expose the oxide semiconductorlayer 23 is provided in the narrow channel width region 25D2. Thereby,in the TFT 20, oxygen is easily supplied to the oxide semiconductorlayer 23, and favorable transistor characteristics are able to berestored.

In this case, it is more preferable that the narrow channel width region25D2 and the aperture 27 are provided in part of the drain electrode 25Dthan that the narrow channel width region is provided in part of thesource electrode 25S. If the aperture 27 is provided in the sourceelectrode 25S, it is difficult to sufficiently secure the retentivecapacity 3C.

The planar shape of the narrow channel width region 25D2 is not limitedto a rectangle as illustrated in FIG. 14, but may be a tapered shape inwhich the width is narrowed as the position thereof becomes apart fromthe source electrode 25S such as a trapezoid, as illustrated in FIG. 16.

FIG. 17 illustrates a planar structure of the pixel circuit 140 usingthe TFT 20 illustrated in FIG. 14 and FIG. 15. The TFT 20 is applicableto both the sampling transistor 3A and the drive transistor 3B, but inparticular, is preferably applied to the drive transistor 3B, since thedrive transistor 3B has a large transistor size.

Modified Example 1-4

FIG. 18 illustrates a planar structure of the pixel circuit 140according to Modified example 1-4. FIG. 19 illustrates an enlargedplanar structure of the drive transistor 3B illustrated in FIG. 18. Inthe pixel circuit 140 and the drive transistor 3B, the oxidesemiconductor layer 23 extends from a section below the drain electrode25D to a section below the power line DSL. The aperture 27 to expose theoxide semiconductor layer 23 is provided in the power line DSL. Thereby,in the pixel circuit 140, oxygen is easily supplied to the oxidesemiconductor layer 23 of the drive transistor 3B, and favorabletransistor characteristics are able to be restored.

The modified example is applicable to both the sampling transistor 3Aand the drive transistor 3B, but in particular, is preferably applied tothe drive transistor 3B, since the drive transistor 3B has a largetransistor size. Further, since the power line DSL has a large linewidth, the aperture 27 is more suitably provided in the power line DSLthan in the scanning line WSL and the signal line DTL.

Modified Example 1-5

FIG. 20 illustrates a planar structure of the pixel circuit 140according to Modified example 1-5. FIG. 21 illustrates a cross sectionalstructure taken along line XXI-XXI of FIG. 20. In the pixel circuit 140and the drive transistor 3B, the oxide semiconductor layer 23 extendsfrom a section below the drain electrode 25D to a section below theretentive capacity 3C. The aperture 27 to expose the oxide semiconductorlayer 23 is provided in the retentive capacity 3C. Thereby, in the pixelcircuit 140, oxygen is easily supplied to the oxide semiconductor layer23 of the drive transistor 3B, and favorable transistor characteristicsare able to be restored.

Second Embodiment

FIG. 22 illustrates a planar structure of the TFT 20 according to asecond embodiment. FIG. 23 illustrates a cross sectional structure takenalong line XXIII-XXIII of FIG. 22. In FIG. 22, the TFT 20 configuringthe foregoing sampling transistor 3A and a capacitor 30 configuring theforegoing retentive capacity 3C in the pixel circuit 140 of the TFTsubstrate 1 are illustrated. The TFT 20 is structured in the same manneras that of the foregoing first embodiment, except that the sourceelectrode 25S and the drain electrode 25D are isolated in the channelwidth direction. Thus, a description will be given by affixing the samereferential symbols to the corresponding elements.

The gate electrode 21, the gate insulating film 22, the oxidesemiconductor layer 23, the channel protective layer 24, and thepassivation film 26 of the TFT 20 are structured in the same manner asthat of the first embodiment.

The source electrode 25S and the drain electrode 25D are isolated by agroove 28 in the channel width direction. In the groove 28, the oxidesemiconductor layer 23 is exposed. Thereby, in the TFT 20, oxygen iseasily supplied to the oxide semiconductor layer 23, and favorabletransistor characteristics are able to be restored.

The channel region 23A is preferably formed in a region within 20 μmfrom the groove 28. Oxygen transfer is transfer in the horizontaldirection through in the oxide semiconductor layer 23 or through aninterface between the oxide semiconductor layer 23 and other layers.Thus, when the channel region 23A is formed in the region within 20 μmfrom the groove 28, effect of the groove 28 is able to be furtherimproved.

Table 1 illustrates a result obtained by examining a relation between achannel width W (a width in the direction perpendicular to the directionin which the source electrode 25S and the drain electrode 25D areopposed to each other, that is, a width in the longitudinal direction ofthe source electrode 25S and the drain electrode 25D) and a channellength L (a width in the direction in which the source electrode 25S andthe drain electrode 25D are opposed to each other), and transistorcharacteristics. As evidenced by Table 1, in the case where W was 20 μmand L was 10 μm as illustrated in FIG. 24, favorable transistorcharacteristics were shown. Meanwhile, in the case where W was 50 μm andL was 10 μm as illustrated in FIG. 25, depression type operation wasshifted to conductor operation. For a reference, in FIG. 26, respectivetransition characteristics in the case where W was 20 μm and L was 20 μm(favorable) and in the case where W was 20 μm and L was 20 μm (conductoroperation) in Table 1 are illustrated.

TABLE 1 L W 5 10 20 10 Favorable Favorable Favorable 20 Depression typeFavorable Favorable 50 Conductor Conductor Conductor operation operationoperation (unit: μm)

In the TFT 20 illustrated in FIG. 24 and FIG. 25, oxygen is suppliedonly from the exposed portion 23B on both ends in the channel widthdirection of the oxide semiconductor layer 23. Thus, the oxygen transferdistance becomes W/2. In FIG. 24, the oxygen transfer distance is W/2=10μm, and favorable transistor characteristics are obtained. Meanwhile, inFIG. 25, the oxygen transfer distance is W/2=25 μm, and the state isshifted to conduction operation. Accordingly, it is found that in thecase where the groove 28 is formed, if the oxygen transfer distance isequal to or less than 10 μm, that is, if the channel region 23A isformed in a region within 20 μm from the groove 28, oxygen is able to besufficiently supplied from the groove 28 and the exposed portion 23B tothe oxide semiconductor layer 23.

The capacitor 30 includes a lower layer electrode formed in the samelayer as that of the gate electrode 21, a capacitor insulating filmformed in the same layer as that of the gate insulating film 22, and anupper layer electrode formed in the same layer as that of the sourceelectrode 25S and the drain electrode 25D sequentially from thesubstrate 10 side.

The TFT 20 and a display unit including the TFT 20 may be manufacturedin the same manner as that of the first embodiment.

In the display unit, as in the first embodiment, a light emitting device3D (organic light emitting devices 10R, 10G, and 10B) emits light, whichis transmitted through the cathode 55, the color filter 72, and thesealing substrate 71 and is extracted. In this case, in the TFT 20configuring the sampling transistor 3A and the drive transistor 3B, thesource electrode 25S and the drain electrode 25D are isolated in thechannel width direction by the groove 28 to expose the oxidesemiconductor layer 23. Thus, by oxygen annealing in the manufacturingstep, oxygen is supplied from the aperture 27 to the absent portion inwhich oxygen is lacked or oxygen is detached in the oxide semiconductorlayer 23, and the transistor characteristics are sufficiently restored.Thus, in the display unit configured by using the TFT 20, low resistanceof the oxide semiconductor layer 23 of the TFT 20 is suppressed, theleakage current is suppressed, and light display with high luminance isenabled.

As described above, in this embodiment, the source electrode 25S and thedrain electrode 25D are isolated in the channel width direction by thegroove 28 to expose the oxide semiconductor layer 23. Thus, oxygen iseasily supplied from the groove 28 to the oxide semiconductor layer 23,and favorable transistor characteristics are able to be restored.Accordingly, if the display unit is configured by using the TFT 20, lowresistance of the oxide semiconductor layer 23 of the TFT 20 issuppressed and thus the leakage current is able to be suppressed, andlight display with high luminance is enabled.

Third Embodiment

FIG. 27 illustrates a planar structure of the TFT 20 according to thethird embodiment of the invention. The TFT 20 is structured in the samemanner as that of the foregoing first and the second embodiments, exceptthat the oxide semiconductor layer 23 is exposed on one side of thedrain electrode 25D. Thus, a description will be given by affixing thesame referential symbols to the corresponding elements.

The gate electrode 21, the gate insulating film 22, the oxidesemiconductor layer 23, the channel protective layer 24, and thepassivation film 26 of the TFT 20 are structured in the same manner asthat of the first embodiment.

A protrusion region 29 in which the oxide semiconductor layer 23 isexposed from an end of the drain electrode 25D is provided along a sideopposed to a side overlapped with the channel protective layer 24 of thedrain electrode 25D. Thereby, in the TFT 20, oxygen is easily suppliedto the oxide semiconductor layer 23, and favorable transistorcharacteristics are able to be restored.

The channel region 23A is preferably formed in a region within 20 μmfrom the protrusion region 29 as in the second embodiment.

The TFT 20 and a display unit including the TFT 20 may be manufacturedin the same manner as that of the first embodiment.

In the display unit, as in the first embodiment, the light emittingdevice 3D (organic light emitting devices 10R, 10G, and 10B) emitslight, which is transmitted through the cathode 55, the color filter 72,and the sealing substrate 71 and is extracted. In this case, in the TFT20 configuring the sampling transistor 3A and the drive transistor 3B,the protrusion region 29 in which the oxide semiconductor layer 23 isexposed from the end of the drain electrode 25D is provided along theside opposed to the side overlapped with the channel protective layer 24of the drain electrode 25D. Thus, by oxygen annealing in themanufacturing step, oxygen is supplied to an absent portion in whichoxygen is lacked or oxygen is detached in the oxide semiconductor layer23, and the transistor characteristics are sufficiently restored.Therefore, in the display unit configured by using the TFT 20, lowresistance of the oxide semiconductor layer 23 of the TFT 20 isinhibited, the leakage current is suppressed, and light display withhigh luminance is enabled.

As described above, in this embodiment, since the protrusion region 29in which the oxide semiconductor layer 23 is exposed from the end of thedrain electrode 25D is provided along the side opposed to the sideoverlapped with the channel protective layer 24 of the drain electrode25D. Thus, oxygen is able to be easily supplied from the protrusionregion 29 to the oxide semiconductor layer 23, and favorable transistorcharacteristics are able to be restored. Therefore, in the case wherethe display unit is configured by using the TFT 20, low resistance ofthe oxide semiconductor layer 23 of the TFT 20 is inhibited, and therebythe leakage current is able to be suppressed, and light display withhigh luminance is enabled.

Modified Example 3-1

In the foregoing embodiment, the description has been given of the casethat the protrusion region 29 is provided on one side of the drainelectrode 25D. However, according to the structure of the TFT 20, asillustrated in FIG. 28 and FIG. 29, the protrusion region 29 may beprovided outside of both the source electrode 25S and the drainelectrode 25D.

Modified Example 3-2

FIG. 30 illustrates a planar structure of the pixel circuit 140according to Modified example 3-2. FIG. 31 illustrates a cross sectionalstructure of the sampling transistor 3A and the signal line DTLillustrated in FIG. 30. In the pixel circuit 140, the oxidesemiconductor layer 23 extends from a section below the source electrode25S or the drain electrode 25D to a section below wirings such as thesignal line DTL and the power line DSL. The protrusion region 29 isprovided in the wirings such as the signal line DTL and the power lineDSL. Thereby, in the pixel circuit 140, oxygen is easily supplied to theoxide semiconductor layer 23 of the sampling transistor 3A or the drivetransistor 3B, and favorable transistor characteristics are able to berestored.

Modified Example 3-3

FIG. 32 illustrates a planar structure of the pixel circuit 140according to Modified example 3-3. FIG. 33 illustrates a cross sectionalstructure of the sampling transistor 3A and the signal line DTLillustrated in FIG. 32. In the pixel circuit 140, an under-wiring oxidesemiconductor layer 23C is provided below wirings such as the scanningline WSL, the signal line DTL, and the power line DSL. The under-wiringoxide semiconductor layer 23C is isolated form the oxide semiconductorlayer 23 as an active layer of the sampling transistor 3A or the drivetransistor 3B by an isolation groove 23D. The wirings such as thescanning line WSL, the signal line DTL, and the power line DSL have awider width than that of the under-wiring oxide semiconductor layer 23C,and cover the entire surface of the under-wiring oxide semiconductorlayer 23C. Thus, in the under-wiring oxide semiconductor layer 23C,oxygen is kept detached in the manufacturing step, and oxygen is notintroduced by annealing for restoring the characteristics of the oxidesemiconductor layer 23. The under-wiring oxide semiconductor layer 23Chas characteristics as a metal, and configures part of the wirings.Further, the under-wiring oxide semiconductor layer 23C is able to beformed with the use of the same mask as that of the oxide semiconductorlayer 23. Thereby, in the pixel circuit 140, without using a pluralityof masks, resistance of the scanning line WSL, the signal line DTL, orthe power line DSL is able to be lowered. Thus, image faults such ascrosstalk and shading caused by wiring resistance are able to besuppressed at low cost.

Module And Application Examples

A description will be given of application examples of the display unitdescribed in the foregoing embodiments. The display unit of theforegoing embodiments is applicable to a display unit of electronicdevices in any field for displaying a video signal inputted from outsideor a video signal generated inside as an image or a video such as atelevision device, a digital camera, a notebook personal computer, aportable terminal device such as a mobile phone, and a video camera.

Module

The display unit of the foregoing embodiments is incorporated in variouselectronic devices such as after-mentioned first to fifth applicationexamples as a module as illustrated in FIG. 34, for example. In themodule, for example, a region 210 exposed from the sealing substrate 71and the adhesive layer 60 is provided in a side of a substrate 11, andan external connection terminal (not illustrated) is formed in theexposed region 210 by extending wirings of a signal line drive circuit120 and a scanning line drive circuit 130. The external connectionterminal may be provided with a Flexible Printed Circuit (FPC) 220 forinputting and outputting a signal.

First Application Example

FIG. 35 illustrates an appearance of a television device to which thedisplay unit of the foregoing embodiments is applied. The televisiondevice has, for example, a video display screen section 300 including afront panel 310 and a filter glass 320. The video display screen section300 is composed of the display unit according to the foregoingrespective embodiments.

Second Application Example

FIGS. 36A and 36B illustrate an appearance of a digital camera to whichthe display unit of the foregoing embodiments is applied. The digitalcamera has, for example, a light emitting section for a flash 410, adisplay section 420, a menu switch 430, and a shutter button 440. Thedisplay section 420 is composed of the display unit according to theforegoing respective embodiments.

Third Application Example

FIG. 37 illustrates an appearance of a notebook personal computer towhich the display unit of the foregoing embodiments is applied. Thenotebook personal computer has, for example, a main body 510, a keyboard520 for operation of inputting characters and the like, and a displaysection 530 for displaying an image. The display section 530 is composedof the display unit according to the foregoing respective embodiments.

Fourth Application Example

FIG. 38 illustrates an appearance of a video camera to which the displayunit of the foregoing embodiments is applied. The video camera has, forexample, a main body 610, a lens for capturing an object 620 provided onthe front side face of the main body 610, a start/stop switch incapturing 630, and a display section 640. The display section 640 iscomposed of the display unit according to the foregoing respectiveembodiments.

Fifth Application Example

FIGS. 39A to 39G illustrate an appearance of a mobile phone to which thedisplay unit of the foregoing embodiments is applied. In the mobilephone, for example, an upper package 710 and a lower package 720 arejointed by a joint section (hinge section) 730. The mobile phone has adisplay 740, a sub-display 750, a picture light 760, and a camera 770.The display 740 or the sub-display 750 is composed of the display unitaccording to the foregoing respective embodiments.

While the invention has been described with reference to theembodiments, the invention is not limited to the foregoing embodiments,and various modifications may be made. For example, the material, thethickness, the film-forming method, the film-forming conditions and thelike of each layer are not limited to those described in the foregoingembodiments, but other material, other thickness, other film-formingmethod, and other film-forming conditions may be adopted.

Further, in the foregoing embodiments, the description has been given ofthe case that the organic light emitting devices 10R, 10B, and 10G havea structure in which the anode 52, the organic layer 54 including thelight emitting layer, and the cathode 55 are layered in this order overthe TFT substrate 1. However, the lamination order is not limitedthereto, as long as the organic light emitting devices 10R, 10B, and 10Ghave the organic layer 54 including the light emitting layer between theanode 52 and the cathode 55. For example, the organic light emittingdevices 10R, 10B, and 10G may have a structure in which the cathode 55,the organic layer 54 including the light emitting layer, and the anode52 are layered in this order over the TFT substrate 1.

Further, in the foregoing embodiments, the description has been given ofthe organic light emitting devices 10R, 10B, and 10G with the specificexample. However, it is not necessary to provide the all layers, andother layer may be further included.

In addition, the invention is applicable to a display unit includingother display device such as a liquid crystal display device, aninorganic electroluminescence device, an electrodeposition displaydevice, and an electrochromic display device in addition to the organiclight emitting device.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alternations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. A thin film transistor comprising, sequentially over a substrate: a gate electrode; a gate insulting film; an oxide semiconductor layer including a channel region; and a channel protective layer covering the channel region, wherein, a source electrode and a drain electrode are formed on the oxide semiconductor layer located on both sides of the channel protective layer, and a protrusion region in which the oxide semiconductor layer is exposed from an end of the source electrode or the drain electrode is provided along a side opposed to a side overlapped with the channel protective layer of at least one of the source electrode and the drain electrode.
 2. The thin film transistor according to claim 1, wherein at least one of the source electrode and the drain electrode has a protrusion region in which the oxide semiconductor layer is exposed from the end of the source electrode or the drain electrode along a side other than the side overlapped with the channel protective layer.
 3. The thin film transistor according to claim 1, wherein the channel region is formed in a region within 20 μm from the protrusion region.
 4. The thin film transistor according to claim 1, wherein: the source electrode and the drain electrode include a metal layer containing aluminum, copper, silver, or molybdenum as a main component, and the source electrode and the drain electrode are made of a single layer film of the metal layer, or a laminated film composed of the metal layer and a metal layer or metal compound layer containing titanium, vanadium, niobium, tantalum, chromium, tungsten, nickel, zinc, or indium as a main component.
 5. The thin film transistor according to claim 4, wherein a layer contacted with the oxide semiconductor layer of the source electrode and the drain electrode is composed of a metal that does not make oxygen detached from the oxide semiconductor layer or a metal compound that does not make oxygen detached from the oxide semiconductor layer.
 6. The thin film transistor according to claim 4, wherein the layer contacted with the oxide semiconductor layer of the source electrode and the drain electrode is composed of molybdenum; an oxide, a nitride, or a nitroxide of molybdenum or titanium; an aluminum nitride; or a copper oxide.
 7. The thin film transistor according to claim 4, wherein an uppermost layer of the source electrode and the drain electrode is composed of titanium; or an oxide, a nitride, or a nitroxide of titanium.
 8. The thin film transistor according to claim 1, wherein the layer contacted with the oxide semiconductor layer of the source electrode and the drain electrode is composed of a conductive metal oxide, a conductive metal nitride, or a conductive metal nitroxide.
 9. A display unit comprising: a thin film transistor; and a display device, wherein, the thin film transistor includes sequentially over a substrate (a) a gate electrode, (b) a gate insulting film, (c) an oxide semiconductor layer including a channel region, (d) a channel protective layer covering the channel region, (e) a source electrode and a drain electrode on the oxide semiconductor layer located on both sides of the channel protective layer, and (f) a protrusion region in which the oxide semiconductor layer is exposed from an end of the source electrode or the drain electrode provided along a side opposed to a side overlapped with the channel protective layer of at least one of the source electrode and the drain electrode.
 10. The display unit according to claim 9, wherein the display device is an organic light emitting device having an organic layer including a light emitting layer between an anode and a cathode. 